Levorotatory form of 5-hydroxytryptophan in Friedreich's ataxia. Results of a double-blind drug-placebo cooperative study.

OBJECTIVE: To study the effect of the levorotatory form of 5-hydroxytryptophan on the cerebellar symptoms of Friedreich's ataxia.

DESIGN: Cooperative double-blind study of the levorotatory form of 5-hydroxytryptophan vs placebo.

SETTING: Twelve centers in research hospitals.

PATIENTS: Twenty-six patients were included; 19 completed the study (mean +/- SD age of patients, 25.9 +/- 8.1 years). Of these 19 patients, eight were treated with placebo and 11 were treated with the drug.

MAIN OUTCOME MEASURES: A semiquantitative scale for kinetic and static ("postural") cerebellar functions and quantitative measurements of time in standard tests that evaluated stance, speech, writing, and drawing.

RESULTS: In the active treatment group, a significant decrease of the kinetic score was observed (P = .03), indicating an improvement in coordination.

CONCLUSIONS: These results demonstrated that the levorotatory form of 5-hydroxytryptophan is able to modify significantly the cerebellar symptoms in patients with Friedreich's ataxia. However, the effect is only partial and not clinically major.